Electrical interconnection is an electrical signal transmission mode that mainly uses a copper wire, for example, inter-server cable interconnection (off-board interconnection), copper wire interconnection (on-board interconnection or inter-chip interconnection) on a printed circuit board (PCB), and multi-core interconnection (on-chip interconnection, which uses copper or other metals as a medium). With the development of semiconductor technologies, a line width becomes smaller in mainstream integrated circuit technologies, and the size and speed of a device gradually reach a physical limit, posing a great challenge to integration. In addition, as a processor speed increases, inherent limitations of electrical interconnection gradually become apparent, and parasitic effects such as parasitic capacitance, delay time, and signal crosstalk of conventional metal interconnection cables become very notable. The electrical interconnection mode cannot implement signal transmission efficiently. Therefore, it is necessary to introduce a new interconnection mode.
Compared with the electrical interconnection mode, optical interconnection is an optical signal transmission mode that uses free space (which may be considered as air or vacuum), an optical fiber, a waveguide, or the like as a medium, and has such advantages as higher bandwidth and greater bandwidth density, lower power consumption, shorter delay, and less crosstalk and electromagnetic interference. Replacing electrical interconnection with optical interconnection in computers has become an inevitable trend.
Currently, there is a through silicon via (TSV)-based optical interconnection system architecture. The TSV technology is the latest technology that implements inter-chip interconnection by means of vertical conduction between chips and between wafers. The optical interconnection system architecture is jointly formed by stacking a bare die of a processor layer, a bare die of a memory layer, and a bare die of an optical interconnection network layer. Three-dimensional (3D) electrical interconnection is implemented between the bare dies at the three layers using a bonding technique and the TSV technology. When an electrical signal of the processor layer or the memory layer reaches the optical interconnection network layer through a TSV, the electrical signal is converted into an optical signal. Transmission of the optical signal is implemented on an optical routing topology network of the optical interconnection network layer, and the optical signal is converted into the electrical signal, which is then sent to the processor layer or the memory layer through the TSV.
In the foregoing optical interconnection system architecture, 3D stacked packaging is implemented completely using the TSV technology, and the optical interconnection in the system architecture is implemented using one optical network layer only, causing a long electrical delay and a great loss. As a quantity of stacked layers increases, the delay and loss of a transmission cable increase, which reduces efficiency of signal transmission.